Many biological materials that are prepared for human, veterinary, diagnostic and/or experimental use may contain unwanted and potentially dangerous biological contaminants or pathogens, such as viruses, bacteria, nanobacteria, yeasts, molds, mycoplasmas, ureaplasmas, prions and parasites. Consequently, it is of utmost importance that any biological contaminant in the biological material be inactivated before the product is used. This is critical for the various biological materials that are prepared in media or via culture of cells or recombinant cells which may be subject to mycoplasma, prion, bacterial and/or viral contaminants.
Peptide-immobilized surfaces have been broadly used to mimic extracellular proteins (such as fibronectin, collagen, vitronectin and lamininin) in the design of scaffold for use in tissue engineering to promote mammalian cell adhesion, proliferation and differentiation. However, in order for these peptide mimetic surfaces to have any therapeutic value they must be sterilized to achieve a sterilization assurance level (SAL) of 10−6, which is the probability of one in a million items being non-sterile.
A conventional method for assuring sterility of a biological production process is aseptic manufacturing. The demands of maintaining a sterile environment throughout this manufacturing process are time-consuming, laborious, and extremely expensive. There are also other sterilization methods to choose from, such as ethylene oxide (EtO), E-beam and Gamma radiation. Ethylene oxide, while being a highly effective method, but leaves behind potentially hazardous residuals and can not reach products in airtight packages. E-beam, while being one of the fastest methods for sterilization, can not penetrate well into dense products or bulk packaging of some products.
Gamma radiation does have some significant advantages over other methods of producing sterile product, such as (1) better assurance of product sterility than aseptic manufacturing; (2) no residue like EtO leaves behind; (3) More penetrating than E-beam; (4) Low-temperature process; (5) Simple validation process. Gamma radiation can also have harmful effects on biological materials, such as proteins or peptides because of free radical formation. Peptide conjugated surfaces have been developed which for the first time provide support for embryonic stem cell proliferation and differentiation in chemically defined media. However, studies showed that after gamma sterilization, the performance of those surfaces were harmed.
In view of the difficulties discussed above, there remains a need for methods of sterilizing cell culture surface compositions or materials that are effective for reducing the level of active biological contaminants or pathogens without an adverse effect on the surface composition or materials.